A352249 Emirps that can be written as p*q+p+q where p and q are emirps.

1439, 1511, 3023, 14447, 16127, 16547, 16883, 19763, 30059, 33623, 35099, 35327, 36251, 38219, 39359, 72911, 75239, 76463, 78623, 94559, 96431, 100799, 103511, 107603, 108191, 108863, 110807, 118583, 119039, 119363, 120539, 121727, 126359, 127679, 128879, 129959, 132299, 132887, 134999, 136403

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(3) = 3023 is a term because 3023 = 17*167+17+167 and 3023, 17 and 167 are emirps.

Maple

revdigs:= proc(n) local L, i; L:= convert(n, base, 10); add(L[-i]*10^(i-1), i=1..nops(L)) end proc:
isemirp:= proc(p) local r;
   if not isprime(p) then return false fi;
   r:= revdigs(p);
   r <> p and isprime(r)
end proc:
E:= select(isemirp, [seq(ithprime(i), i=1..10^4)]):
nE:= nops(E): N:= E[1]*E[-1]+E[1]+E[-1]:
S:= {}:
for i from 1 to nE do
  for j from i+1 to nE do
    x:= E[i]*(E[j]+1)+E[j];
    if x > N then break fi;
    if isemirp(x) then S:= S union {x} fi;
od od:
sort(convert(S, list));

Crossrefs

Cf. A006567.

Sequence in context: A221004 A204862 A227494 * A351677 A101798 A081426

Adjacent sequences: A352246 A352247 A352248 * A352250 A352251 A352252

Keyword

nonn,base

Author

J. M. Bergot and Robert Israel, Apr 17 2022

Status

approved